Let us sharply distinguish here between two epistemological positions. The first, extreme physicalism, asserts that only physics and its branches can be considered sciences.15 Hence, all observations must be formulated in the language of physics. The second position, a sort of liberal empiricism, recognizes a variety of legitimate methods and languages within the family of science.16 Indeed, since different types of problems are considered to require different methods of anal- ysis, a diversity of scientific methods and expressions is not merely tolerated, but is considered necessary. According to this position, the value, and hence the scientific legitimacy, of any particular method or language depends on its pragmatic utility, rather than on how closely it approximates the ideal model of theoretical physics.